Mobile thermoforming apparatus and method

ABSTRACT

Thermoforming apparatus and method for continuously thermoforming a continuous web or sheet into a self-supporting, protective crop cover, preferably hat-shaped in cross-sectional configuration. The apparatus utilizes counter-rotating forming means, specifically sets of wheels on two adjacent axles, each set having primary forming wheels fixed to the axle and cooperative idler forming wheels freely rotating thereon, each idler wheel cooperating with a primary wheel on the opposing axle. Heat is supplied to the forming means, preferably by circulation of heated fluid. Forming pressure is supplied by shifting the forming means into cooperative relationship. Such a crop cover is continuously formed by simultaneously heating and bending the sheet or web material into the configurated shape, and is continuously positioned over the row as formed, and anchored by pushing dirt onto its flanged edges.

ilriited States Patent [1 1 Havfland, Jr. et al.

[ MOBILE THERMOFORMING APPARATUS AND METHOD [75] Inventors: James B. Haviland, Jr.; Charles R.

Balkema, both of Grand Rapids, Mich.

[73] Assign'ee: ,Haviland Agricultural Chemical Company, Grand Rapids, Mich.

[22] Filed: Sept. 30, 1971 [21] Appl. No.: 185,252

Related US. Application Data [62] Division of Ser. No. 15,648, March 2, 1970, Pat. No.

FOREIGN PATENTS OR APPLICATIONS 782,115 9/1957 Great Britain 1 June 12, 1973 Attorney-Price, Heneveld, Huizenga and Cooper [57] ABSTRACT Thermoforrning apparatus and method for continuously thermoforming a continuous web or sheet into a self-supporting, protective crop cover, preferably hatshaped in cross-sectional configuration. The apparatus utilizes counter-rotating forming means, specifically sets of wheels on two adjacent axles, each set having primary forming wheels fixed to the axle and cooperative idler forming wheels freely rotating thereon, each idler wheel cooperating with a primary wheel on the opposing axle. Heat is supplied to the forming means, preferably by circulation of heated fluid. Forming pressure is supplied by shifting the forming means into cooperative relationship.

Such a crop cover is continuously formed by simultaneously heating and bending the sheet or web material into the configurated shape, and is continuously positioned over the row as formed, and anchored by pushing dirt onto its flanged edges.

1 Claim, 12 Drawing Figures PATENTED JUN 1 2975 SIEHING BACKGROUND OF THE INVENTION This invention relates to apparatus and a method for thermoforming a continuous web or sheet into a configurated, self-supporting crop cover, preferably hat shaped in cross section. I I

It is customary to place protective materials over crops to prevent damage from frost and other weather factors. To avoid the cost of hand labor and to provide maximum efficiency, various machines have been designed for continuously laying down such protective covers. However, prior known machines have not been capable. of laying down a self-supporting, continuous crop row cover which is hat-shaped in cross section, and which projects above the ground and crop without any additional supporting framework of the type dis- It is an object .of this invention to provide an apparatus and method for continuously thermoformingsheet material into a configurated crop cover to be .placed over row crops for protection. I

It is a-related object of the invention to provide apparatus and a method of theabove character adapted to continuous thermoforming of a thermoplastic synthetic material into a strong, stable crop cover that is selfsuppo'rting, enabling it to project above the crop row without additional supporting means such as a frame.

Still another object of the invention is to provide apparatus and a method of the above character enabling the thermoforming operation to be performed in situ as the apparatus is mov e d along a row of ,crops to be laid down in position while spaced above the crop, and anchored astraddle the crop row. i

. Yet another object of the invention is toprovide apparatus and a method of the above character which are relatively inexpensive to utilize.

The novel apparatus employs special,.cooperative, rotational, thermoforming means that continuously receive flat webstock .and discharge a specially configurated, self-supporting croprow cover.

The thermoforming means employs counter-rotating, cooperative heated forming elements on spaced rotation axes. The elementsarepreferably heated wheels on spaced axles, with larger wheel means on one axle cooperating with smaller wheel means on the other axle to form the top of a hat-shaped configuration, and smaller wheel means on said one axle cooperating with larger wheel means on said other axle to form the straddling lower flanges on the hat-shaped configuration. A special heated convergent feed tunnel is oriented toward the wheel means. 7

When used to form the crop cover in situ, means are provided for moving the apparatus along a row of crops and for driving the axle in response to this movement. When so used, the continuously thermoformed sheet drops over the row as it is formed from one end of the sheet to the other, and earth ispushed overthe flanged edges of the thermoformed member to retain the cover in place.

Other objects and advantages will become apparent upon reference to the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary, perspective view of apparatus constructed in accordance with the invention;

FIG. 2 is an end perspective view of the apparatus in FIG. I as seen from the downstream end;

FIG. 3 is the opposite end perspective view of the ap paratus in FIG. 2; 7

FIG. 4 is a fragmentary perspective view similar to FIG. 2, but enlarged to show more details;

FIG. 5 is a fragmentary perspective view similar to FIG. 3, but enlarged to show more details;

FIG. 6 is a side perspective view of the apparatus in the previous figures;

FIGS. 7 and 8 are fragmentary perspective views taken from the opposite side as shown in FIG. 6, illus trating the alternate positions for the frame mounting the top axle subassembly;

FIG. 9 is a schematic view illustrating the path of the heating fluid for the apparatus;

FIG. 10 is a perspective view of the pre-heating and pre-forming tunnel of the apparatus;

FIG. 11 is a fragmentary elevational view illustrating the relative positioning of the forming wheels of the device when engaging the web or sheet material; and

FIG. 12 is a schematic plan view illustrating use of the apparatus and the novel method.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to the drawings, apparatus 10 is for thermoforming a continuous web 20 of thermoplastic synthetic material such as foamed polystyrene, into a crop row cover 22 having a hat-shaped cross section, the thermoformed cover being designed to protect a row of crops 24 while spaced thereabo've, yet being held in position by dirt 26 pushed over and onto the crop-straddling flanged edges of the cover (FIG. 12).

The apparatus (FIG. 1) includes a general framework 30 of a traveling vehicle of any suitable type, with at least two axles 32 and 34 journalled thereto. A plurality of heated wheels or wheel-like members 40, 40a, 60, 60a, and 70a constitute forming means, the wheels being mounted on axles 32 and 34. At least one of the axles is driven, as by a running wheel 120 engaging the ground. The axle 34 is mounted above axle 32 and for reciprocation toward and away from axle 32 by means of a sub-frame designed to allow its weight and the weight of axle 34 and its wheels to bias such down against the sheet material in cooperative relationship with the wheels on axle 32 thereunder.

A plurality of heating passageways is provided in the wheels and axles, communicant with a heat supply line 9 to feed hot fluid to these passageways (FIG. 9).

At various places in this specification, relative directions and positions such as peak, bottom," highest point, lower," and upper are utilized. These are not absolute terms but are to be construed with respect to the orientation of the structure as described.

SHEET FEED The apparatus thermoforms a web continuously, such web preferably being fed from a roll 160 of the sheet or web material mounted on a shaft 162 conventionally journalled to any convenient portion of frame 30 (FIG. 1).

PREFORMING AND PREI-IEATING TUNNEL Positioned downstream of roll 160 is a tunnel or inverted channel 170 which receives the flat stock and curves it into a generally parabolic shape, convexly upward and concavely downward. Tunnel 170 (FIGS. 3, 4, 5, and is positioned upstream of axles 32 and 34 and the forming wheels thereon, to assist in the feeding of the sheet between the wheels. The channel also has a preheating function (hereinafter described) which enables the web to be readily curved thereby and to partially prepare the material for the forming wheel. The upstream end 172 of the channel is curved in cross section, with the tunnel converging to the hat-shaped downstream end 174 positioned adjacent the nip of the wheels. The peak 176 of the hat-shaped end 174 is aligned with the highest point of the primary wheels 40 on lower axle 32. The bottom edges 178 (FIG. 4) of channel 170 are aligned with the highest point of sleeve 70 of the secondary wheels 60 on lower axle 32. The web material is fed directly from tunnel 170 into the nip of the forming wheels.

FORMING WHEEL MEANS The two sets of forming wheels on the two axles are movable with respect to each other, together and apart.

- This is done by mounting one set on a movable frame portion and the other set on thefixed frame portion. v

Turning now to FIGS. 2 through 5, and FIG. 11, frame comprises a base 35, uprights 36, and a subframe 37 welded to base and uprights 36. It is within sub-frame 37 that the axle 32 is journalled. The journalling of the axles 32 and 34 is conventional, and accordinglyis not further described.

On axle 32, a set of primary wheels and secondary wheels 60 are mounted, wheels 40 being mounted between wheels 60, the latter being idler wheels. That is, wheels 40 are fixably mounted to axle 32, while wheels 60 are freely rotatably mounted, for purposes hereinafter described. The outer annular axial faces 62 of idler wheels 60 have a frustoconical surface (FIG. 11). The corresponding inside faces 64 of primary wheels 40 have a similar tapered surface.

Two wheel-extension sleeves 70 are mounted immediately adjacent to and axially outside of idler wheels 60. Sleeves 70 are also freely rotatably mounted upon axle 32, for a reason hereinafter described.

The second, upper axle 34 has a set of primary wheels 40a and secondary wheels 60a mounted thereon the latter including wheel-extension sleeves 700. Primary wheels 4011 are fixed to axle 34. Idler wheels 600 are rotatably mounted on the axle adjacent to and between primary wheels 40a. Idler wheels 60a have frustoconical, axially inner faces, cooperative with correspondingly tapered faces on the outer faces of the primary wheels mounted on axle 34. Sleeves 70a are combined into one freely rotatable sleeve between two idler rollers 60a.

Referring now to FIG. 11, the cooperation between the primary wheels and the idler wheels and sleeves will become apparent; Thus, primary wheels 40 cooperate with idler wheels a and sleeve a, while primary wheels 40a cooperate with idler wheels 60 and sleeve 70 to bend the sheet material into the hat-shaped cross section when the sheet feeds into the nip of the wheels. That is, surfaces 62 of the idler wheels and surfaces 64 of the primary wheels press on opposite sides of the sheet material while edges 72 of primary wheels 40a and 40 press the sheet material against the immediately adjacent sleeve 70 or 70a, respectively, on the opposite axle. Because the exterior diameter of the primary wheels is so much larger than the exterior diameter of either of the cooperating idler wheel or sleeve, the interior diameter of the sleeve and of the idler wheel will rotate considerably faster than the axle on which the sleeve or idler wheel is mounted. Thus, as indicated above, the idler wheels and the sleeves are freely rotatably mounted on their axles.

The wheels and sleeves constitute bending surfaces, which, because of their rotation, are substantially free from friction due to slippage, as the wheels engage rather than slide against, the underside of the sheet ma terial 20. Thus, the sheet material is not torn as it is fed through the bending wheels. This is particularly important with respect to foam stock material.

To maintain the correct positioning of the idler wheels and the sleeves, spacing sleeves 74 and 74a are provided on the axles 32 and 34, respectively. The spacing sleeves can be fixed to the axles or freely rotated thereon.

ENGAGING MEANS FOR THE FORMING MEANS end now to FIGS. 6 through 8, axle 34 is journalled to sub-frame at end 82 thereof, the opposite on 84 being pivotally mounted to sub-frame 37 on a shaft 85 journalled thereto. (See FIG. 2). A U-bar 86 connects the ends 82 of the sub-frame, the U-bar extending over primary wheels 40a. To raise and lower sub-frame 80 and axle 34 journalled thereto, a lever 90 is pivotally mounted at 91 on an upright 92 on sub-frame 37. The lever has a connecting rod 96 pivoted thereto at a point 94 intermediate the ends of the lever. Connecting rod 96 comprises a threaded bar 98 and an adjustable connecting bar 100. The bar 98 is bolted to U-bar 86 at 102, so that when handle 90 is pivoted about its pivot 91, connecting link 96 causes U-bar 86 and sub-frame 80 to raise and lower with respect to sub-frame 37 and axle 34. As shown in FIG. 8, lever 90 is released so as to lower sub-frame 80 and axle 32 into the engaging position for pressing against the sheet material to be thermoformed.

An upright is welded to sub-frame 37 and has positioned thereon a limiting bolt 112, the purpose of which is to limit the downward pivoting or reciprocation of sub-frame 80 on shaft 85.

DRIVE MEANS As indicated above, frame 30 normally is to be moved along the ground surface with vehicular means (not shown in detail) and driven as by wheel mounted on frame 30 (FIG. 1) by mount 31. The wheel 120 comprises a tire 122 fixably mounted to a spindle axle 124, journalled within a hub 126 attached to mount 31.

A sprocket 128 is fixed to axle 124 to drive a chain 130 which in turn drives a sprocket 143 on jack shaft (FIGS. 1 and 6). Sprocket 142 on shaft 140 drives a chain 144 which counter-rotatably engages sprockets 146 and 148. Sprocket 146 is mounted on shaft 32,

while sprocket 148 is mounted on shaft 85. (See FIG.

6). The shaft 85 also has a sprocket 152 mounted at its opposite end (FIG. 7), in turn driving a chain 154 which drives a sprocket 156 mounted on axle 34.

Thus, axles 32 and 34 are counter-rotatably driven, along with the primary wheels affixed thereto by wheel 1 20.

HEATING can be ethylene glycol. The fluid (FIG. 9) is supplied from a convenient heating source (not shown) to hose 190, a gauge 194 indicating the temperature and/or pressure of the fluid.

From point 192 where hose 190 attaches to axle 32, the passageway of the heating fluid is through the center of axle 32 to a point near the middle of the length of the axle. (See FIG. 9). At this point, the fluid is conducted through a tube 196 (FIG. 4) joined to axle 32 at a nipple 197 and extending radially out into the rim of one primary wheel 40 positioned adjacent tube 196. The tube 196 extends around in this primary wheel rim at least approximately once, at which point it emerges and-merges with tube 198 which extends around the rim of the adjacent primary wheel (FIG. 2). Tube 198 coils around at least one, and extends radially back to axle 32 as tube 200 (FIG. 7). The heating fluid then flows out the opposite end 202 of axle 32 to a line 204 which attaches to a passageway 206 mounted inside tunnel 170 for the preheatingfunction.

' Passageway 206 (FIG. 10) is a tube similar to tubes 196, 198, and 200, previously described, but mounted within channel 170 on its interior surface. Tube 206 is bent to be positioned adjacent the portions of the channel having the greatest rate of curvature, thus delivering the heat to the portions of the sheet material which are to take on the greatest curvature. As will be readily apparent, these portions are the places where the bottom edge 178 of the channel joins the side portions, and where the side portions of the channel join the top or peak portion 176.

After passing through tube 206, the heating fluid is then carried by line 210 to axle 34 at end 212 thereof (FIG. 9). The heating fluid is then carried down a passageway in axle 34 until it reaches a position exterior to the first primary wheel 40a on that axle, at which point a tube 214 is attached to the axle and carries the heating fluid therefrom to the circumference of primary wheel 40a. The tube 214 is wound around and within the circumference of the primary wheel 400 at least once, thereafter exiting through to the opposite side of the-primary wheel to a nipple 216 where it joins axle 34 once again. The heating fluid then proceeds again through axle-34 to a nipple 218 which-joins to tube 220 that extends to the rim of the second primary wheel 40a. The tube 220 winds around and within the circumference at least once, at which point it exits out the opposite side of the second primary wheel and joins once again to axle 34 at nipple 222. The heating fluid then exits out of axle 34 at end 224 and from there out a return line 228. All of the heating tubes described above are preferably formed from material of high heat conductivity, such as a copper alloy. It will be readily appreciated that because of the passageway of the heating fluid through the axle at the point where the idler wheels are positioned, the idler wheels also will be heated by the fluid. The flow of the heating fluid through the serially connected passageways causes transfer of heat to the sheet material as it passes through the wheels, to inelastically retain the hatshaped cross section forced upon it by the cooperating nature of the bending wheels 40, 40a, 60, and 60a, and sleeves and 70a.

METHOD The aforedescribed apparatus is utilized to thermoform thermoplastic sheet material continuously to produce in situ a continuous cover for dropping over rows of crops in fields. To this end, the roll is unwound (FIG. 12) and fed continuously through tunnel and to the wheels 40, 40a, 60 and 60a causing a simultaneous heating and bending of the thermoplastic materials into the hat-shaped cross section desired for the cover. Thereafter, cover 22 so thermoformed drops continuously over a row of crops as the apparatus moves along the row of crops. The generally coplanar (FIG. 11) flanged edges rest on the ground astraddle the row, while the self-supporting formed cover extends to a spaced position above the crop row. Plow means 230 can be attached to the frame or mounted on a separate apparatus to push earth up and over the flanged edges of the thermoformed cover, to retain the cover in place.

Conventional foamed polystyrene sheet is the preferred web stock material due to its resistance to weathering, its appropriate light transfer, and its selfsupporting nature when so formed. Other thermoplastic material capable of being inelastically formed into a cross section similar to a hat-shape can be utilized in the apparatus and in accordance with the abovedescribed method. Examples of such materials are foamed polyvinyl (PVC and/or PVA), non-foam polyvinyl, non-foam polystyrene, or any of several other thermoplastic materials well known in the art.

The cross section of the formed member, as is shown, has a top panel joining a pair of side panels arranged in frusto-pyramidic fashion, with oppositely extending flanges at the lower edges of the side panels. The flanges are formed between the outer peripheral surfaces of primary wheels 40a and the peripheral surfaces of secondary sleeves 70.

OTHER EMBODIMENTS Although the invention has been described in connection with a preferred embodiment, it will be readily appreciated that many variations are possible which will provide an equivalent structure and method. For example, the primary wheels 40 can be combined into a single wheel on the axle 34 having a width which will span the same distance as presently spanned by the two wheels 40. Such a single wheel would require a heating tube around the circumference of both sides as is accomplished by having two separate wheels in the present disclosure. Still another modification could utilize whcels shaped so as to produce a hat-shaped cross section having varying dimensions or curved surfaces.

The apparatus can also be utilized to continuously produce thermoformed items having end uses other than a crop cover.

Accordingly, it is intended that the invention shall cover these additional equivalent structures and methods, unless the following claims expressly state otherwise.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A method for protecting row crops with a row cover without requiring additional supporting means for the cover, comprising:

a. continuously heating a continuous web of thermoplastic material to a temperature sufficient to temporarily soften it and bending and thereby thermoforming the continuous web of thermoplastic material into a self supporting hat-shape cross-sectional configuration having oppositely extending edge flanges which are generally coplanar to rest in c0- planar fashion flat on the ground surface astraddle a crop row, and having strong, upstanding thermoplastic side walls which are self supporting without additional supporting means;

b. continuously dropping the self supporting thermoformed structure over a crop row as the structure is thermoformed, with the opposite edge flanges of the self supporting structure resting in coplanar fashion on the ground and the center spaced above the ground c. and pushing earth on top of the edge flanges of the structure to retain the structure in place with respect t0 the Crop l'OW. 

1. A method for protecting row crops with a row cover without requiring additional supporting means for the cover, comprising: a. continuously heating a continuous web of thermoplastic material to a temperature sufficient to temporarily soften it and bending and thereby thermoforming the continuous web of thermoplastic material into a self supporting hat-shape crosssectional configuration having oppositely extending edge flanges which are generally coplanar to rest in coplanar fashion flat on the ground surface astraddle a crop row, and having strong, upstanding thermoplastic side walls which are self supporting without additional supporting means; b. continuously dropping the self supporting thermoformed structure over a crop row as the structure is thermoformed, with the opposite edge flanges of the self supporting structure resting in coplanar fashion on the ground and the center spaced above the ground c. and pushing earth on top of the edge flanges of the structure to retain the structure in place with respect to the crop row. 